1. Field of the invention
This invention relates to a process for converting coal to low-sulfur and low-ash gaseous, liquid and solid fuels, and more particularly, to a process for supplying the energy requirements of a steel plant from an ash- and sulfur-containing coal.
2. Description of the Prior Art
The primary source of energy for the steel industry continues to be coke for the blast furnace. The conventional method for coke manufacture, that is, by slot ovens, requires a blend of high and low volatile coals of proper swelling properties to produce a strong coke without damaging the ovens. Beyond these physical properties, there is a need for desirable chemical properties (i.e. low ash and sulfur content) to permit low-cost production of high quality hot metal. With the continued expansion of the world's productive capacity for steel, a growing shortage of good metallurgical coals is developing, particularly those having the essential low volatile coal ingredients. Low-sulfur coals also are in short supply because the electric utilities now compete for such coals to satisfy environmental requirements.
In addition to the energy supplied by coke and coke oven by-products, the steel industry consumes liquid and gaseous fuels for blast furnace injection, soaking pits, reheat furnaces, steam and power generation, etc. Future supplies of these fuels are also in jeopardy.
There are extensive reserves of coals in the United States, and in other parts of the world as well, sufficient in fact, to satisfy a substantial part of the energy needs of the world for centuries to come. Unfortunately, these coals in their indigenous state are not suitable for use either as clean fuel, i.e. low ash- and low sulfur-containing, or as feedstock for coke manufacture.
Accordingly, the primary object of the present invention is to provide a process for converting any coal, by itself, whether it be caking or non-caking, low sulfur or high sulfur, low ash or high ash, low volatile or high volatile, to a desired spectrum of clean gaseous, liquid and solid fuels. The solid fuel, for purposes of a steel plant, is coke, or formcoke. The term "formcoke" defines coke obtained by the calcination of preformed or preshaped carbonaceous solids and is used to distinguish from coke obtained as broken pieces of all sizes and shapes from conventional coke ovens.
The prior art is represented by the following patents and publications:
______________________________________ U.S. 1,925,005 Rose Aug. 29, 1933 2,166,321 Pott July 18, 1939 2,664,390 Pevere et al. Dec. 29, 1953 2,686,152 Franke Aug. 10, 1954 3,018,242 Gorin Jan. 23, 1962 U.S. 3,240,566 Bullough et al. Mar. 15, 1966 3,401,089 Friedrich et al. Sept. 10, 1968 3,562,783 Gorin Feb. 9, 1971 3,748,254 Gorin July 24, 1973 3,791,956 Gorin et al. Feb. 12, 1974 German Pat. No. 320,056 - Rutgerswerke AG - Apr. 21, 1920 "Process for the Solvent Extraction of Coal" Bureau of Mines Information Circular - I.C. 7420 (Oct. 1947) "Pott-Broche Coal-Extraction Process and Plant of Ruhrol G.m.b.H., Bottrop-Welheim, Germany". ______________________________________